| 摘要 |
PROBLEM TO BE SOLVED: To provide a core bar set, wherein a variance in forming load required for pressing-in is restrained and the facility cost can be reduced. SOLUTION: The core bar 10 is provided with a bar material 11 having the maximum cross section region smaller than the minimum cross sectional area region of the hollow part of a pipe P and projected parts 21-23 projected on the bar material 11 and gradually larger of the maximum projected amount from No.1 to No.M and setting this maximum width to the constant, and the bar material is set to the projected parts 21-23 as the maximum width so that the width is gradually narrowed toward the reverse side to the tooth die 130. COPYRIGHT: (C)2009,JPO&INPIT
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